600W at night - What could possibly draw so much power?

I’ve had my Sense for 2+ weeks now, and at night, it’s telling me my power consumption does not go below 600 W. Been scratching my head as to what could possibly be drawing that much power but to no avail. I have several always plugged-in devices (smart switches, lighted GFCI outlets, fridge/freezer, security cameras, landscape lights, …). I listed all in Excel, and added up their rated/max power, and came-up very short of the 600W.

I’ve read in another thread that some houses have ‘constant-on’ devices such as an attic fan that draw 200W … but can’t think of any such thing in my house.

Any thought as to what could be drawing so much power … or maybe some errors with the Sense?

I’m leaning to two possible culprits:

  1. The Sense CTs are not properly calibrated (long shot)
  2. Something else at home drawing power … and can’t figure out what it is.

How do I solve this? Well, been thinking of 2 approaches:

  1. I have the extra CTs for monitoring 2 additional circuits … I could move those around, two circuits at a time, and monitor their draw over 2 hours. That will take a lot of time as I have about 30 breakers and no guarantee I can catch the power hogs, especially if their power draw is intermittent/transient.
  2. Invest in a second monitor (made by a competitor of Sense) that uses 16 CTs, and monitor many of the circuits all at once.

did you include any laptops that are constantly/always plugged in? Any fish tanks with water heaters?
My lowest power usage is around 400W and I have a relatively small house, FWIW.

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Two thoughts:

  1. Is your Always On running at about 600W, or are you making your determination by looking at the Power Meter ?
  2. Many devices from TVs to Stereos to Appliances have small (3-10W) Always On components to them to keep the logic board powered up. Things like thermostats/finance and garage door openers might even run a little higher depending on age. I have used a “traveling smartplug) to look at many of the devices in my house. You might also have things like recirc pumps for hot water (50W) ?
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You say 600w at night. meaning your Always On number is 600w, or if you go look at the power meter for night time, the lowest you can find is 600w? (one would think they would be similar, but its possible they aren’t).

Can you post a photo of your power zoomed to just an over night period? It won’t tell you WHAT is using power overnight, but just by looking at the power graph, you can learn a little about how much the power fluctuates overnight.

While I guess in theory your CT’s could be mis calibrated, you should see that in other places. When you align Sense usage to your power bill, are they close. If so, I doubt it is a calibration issue.

Something to note about the Always On calculation - it is a calculation, so you won’t see instant changed. but the power meter is live.

Without spending any more money, you could start by just turning off some breakers over night while you are sleeping. Then in the morning, turn them on and go check your power meter to see if the overnight meter shows any real difference. I realize that this isn’t ideal as I’m sure there aren’ t many breakers you can leave off without impacting life, but its a free way, and if you aren’t already familiar with what each of your breakers does, you will learn in the process and start to whittle things down. Unless there really is a single device you don’t know about, this should at least help you track some of the usage down to individual circuits and then you can go the next level of what is on each circuit and is there anything that can be adjusted.


Sense is generally pretty accurate. I would expect it to have less than 1% errors.
You could confirm the overnight usage based on your meter(if it is accurate enough). Check it before you go to bed and when you wake up. See if it correlates with the Sense data.

As others have stated, there can be many vampire loads that we don’t often think about.
well pumps, sump pumps, pool pumps, garden feature pumps
electric floor heating (we have it in one of our bathrooms and didn’t even know)
old electrical devices can use a lot of power in standby mode (newer devices should use less than 1W in standby).
cable boxes are notorious power hogs.
incandescent lights, especially if they are always on.
Engine block and fishtank heaters (mentioned above)
PCs left on. The power varies enormously as later models tend to power down(this can be overridden in settings).
Electric hot water heaters
Old alarm systems, or any system over 10 years old should be looked at for efficiency.
Hot tub and pool heaters.
Fish tank or terrarium heaters.

Some people have gone to the trouble to switch off breakers to try to work out which circuit is involved. This is where sense excels as it gives virtually instantaneous power readings.

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Maybe old outdoor flood lights with motion sensors?

Thank you all. Many useful suggestions in your replies. I got 4 smart plugs (TP-Link) coming in few days. Will install them near ‘suspicious’ appliances, and will then do a more thorough analysis. The house is about 3000 sq.ft. and … we’ll see.

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Here is one I totally forgot about : a Radon fan, that’s drawing around 75W

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I redid all the outdoor lighting, and it’s drawing at most 100W, a combination of lanterns and landscape lights, all LEDs.

Would be nice/useful to collect some stats as to House Size vs. Average monthly kWh vs. night time consumption … then one can start digging for patterns/usages.

3000 sq ft / 1300 kWh / 600 W

In the meantime you can start flipping breakers and watching the meter. Just don’t flip the wifi breaker or the sense one

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Yes … it happened already. I need the modem/router on a dedicated circuit.

By looking at the Power Meter … at night it does not drop below 600W. I did some calc based on ‘max’ the attached devices can draw (max ratings of the corresponding power adapters).

  1. Radon Fan - 80W
  2. Computers on StandBy - 50W
  3. TV+Network Drive + UPS + Router - 50W
  4. Wyze Cameras - 100W
  5. Aquarium+Heater - 200W
  6. Smart Switches & lighted plugs - 20W

It’s inching closer to 600W already … The two I intitially did not account for were the aquarium and radon fan… Time to ditch the fish.

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Nice job on the accounting. What does Always On say ???

Can’t answer now as I ‘reset’ all data. I’ve been moving CTs and smartplugs around over the past few days, and data got a bit scrambled. So, I did reset it, and it still has not detected everything. Currently, my Always-On is at 480W.

Give it a couple days, but Always On is probably a more accurate indicator of your min. I have a bunch of smart plugs at work, so I get a pretty good view of a bunch of devices that are always on and their standby power.

Thank you for sharing. That’s very useful data that you’re showing. Once mine populates, I’ll upload something similar, just so the community has a ‘reference’.

This leads me to another question: Those devices hat are Always-On i.e., never turn-on or shut-off … can Sense still detect them? My understanding is that Sense detects devices based on their ‘signatures’ when they turn on/off. If that is true, then the Always-On devices cannot be detected, unless fed from a smart-plug. For example, my Radon Fan is hard wired and always on, on the same circuit for the basement lights. Lights can be switched on/off, but not the fan. Am I correct in assuming I’ll never get a fair reading of what the fan consumes?


Maybe you have already accounted for these type of electronics, but don’t overlook adding to your “Always On” list:

  • Hardwired Smoke Detectors (the wireless style consume more energy)
  • Battery chargers - garage tools, car battery trickle chargers, etc.
  • Electronic Thermostats
  • Doorbell transformers
  • Clocks

And all the little special LED lights on items/devices that just show they are “plugged in”. I tallied up all my “Always On” devices and found that SENSE was right on target for my usage. I think my estimated/guessed/calculated value was only off by 20 watts from the SENSE value. In some cases I used a Kill-A-Watt monitor to determine how much a particular “Always On” device was using. Good Luck!

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Yes, Sense relies on finding on and off transitions,. It won’t find devices that don’t transition between off and on and then on to off. It also won’t find always on components of devices it does detect (is can see my furnace blower turning on and off, but not the 8W that continuous go to the logic board and thermostat). Plus there are lots of electronics that don’t have a nice clear on and off signature. Once again, I would recommend using a traveling star-lug to look at many fo the behaviors of 120V plugin device in your house to get an idea of where you might want to use more smart plugs.

Thank you, and you’re absolutely correct. I’ve forgotten about my Nest thermostats, multiple smoke/CO detectors, Ryobi chargers … etc. Amazing how many devices use electricity. I’ll keep hunting for devices I have not thought of.

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